1. Field of the Invention
The present invention relates to a method for manufacturing a honeycomb structure and a material composition for a honeycomb fired body.
2. Discussion of the Background
Recently, particulates, such as soot, contained in exhaust gases that are discharged from internal combustion engines of vehicles, such as buses and trucks, and construction machines and the like have raised serious problems as contaminants harmful to the environment and the human body. There have been proposed various honeycomb filters using a honeycomb structure made from porous ceramics, which serve as filters capable of capturing particulates in exhaust gases to purify the exhaust gases.
Conventionally, in order to manufacture a honeycomb structure made from silicon carbide as those mentioned above, first, for example, silicon carbide powder, a binder, a dispersant solution and the like are mixed to prepare a material composition. This material composition is then continuously extrusion-molded, and the extruded molded body is cut into a predetermined length to manufacture a rectangular pillar-shaped honeycomb molded body.
Next, the honeycomb molded body obtained above is dried by using a microwave drying apparatus or a hot-air drying apparatus, and the predetermined cells thereof are sealed so that either one of the end portions of each of cells is sealed, and then a degreasing treatment and a firing treatment are carried out on this to manufacture a honeycomb fired body.
Thereafter, a sealing material paste is applied to side faces of the honeycomb fired bodies to bond the honeycomb fired body to one another so that an aggregated body of the honeycomb fired bodies in which a number of honeycomb fired bodies are combined by interposing the sealing material layer (adhesive layers). Next, a cutting process is carried out on the resulting aggregated body of the honeycomb fired body, that is formed into a predetermined shape such as a cylindrical shape, a cylindroid shape and the like by using a cutting machine and the like to form a honeycomb block, and lastly, a sealing material paste is applied to the periphery of the honeycomb block to form a sealing material layer (coat layer), thereby completing the manufacturing of a honeycomb structure.
In the case where a honeycomb structure is manufactured by the above-mentioned process, usually, manufacture of the honeycomb structure has been carried out using a commercially available silicon carbide powder. However, in the conventional method for manufacturing a honeycomb structure, there have been cases where, upon using a commercially available silicon carbide powder, sintering of silicon carbide does not proceed well in the firing process, and thus occasionally there may be difficulty in manufacturing a honeycomb structure with sufficient strength.
As a method for manufacturing a honeycomb structure of this kind, Japanese Unexamined Patent Application Publication No. 2002-265270 discloses a manufacturing method using, as a silicon carbide powder, silicon carbide powder containing 0.1 to 5% by weight of silica. The contents of Japanese Unexamined Patent Application Publication No. 2002-265270 are incorporated herein by reference in their entirety.